1. Field of the Invention
The present invention relates to a detection of a jet failure of a nozzle in an ink jet printer.
2. Description of the Related Art
In an earlier developed ink jet printer, an image is recorded by jetting ink droplets onto a recording medium from a plurality of nozzles which use a thermal system or a piezo system actuated according to jet signals based on image signals. In the ink jet printer, fixing of ink near nozzles due to drying or increased viscosity of the ink in a case of being left for a long period of time without being used or adhering of impurities (foreign particles) or the like to the nozzles would cause clogging of the nozzles, which results in a failure of jetting ink droplets from the nozzles in spite of normally outputting ink jet signals from a drive circuit, that is, a jet failure of ink from the nozzles (hereinafter, referred to as nozzle clogging). The nozzle clogging would cause a deterioration of print quality such as generating a blank in a printed character or image, which is recognized as a white stripe, or causing difference of reproduced color in each recorded image due to a lack of ink color material. Therefore, an optical detection section as a detection section for detecting such the nozzle clogging has been disclosed.
For example, disclosed is an ink jetting condition detection method for detecting nozzle clogging by changing a detection timing with a photo sensor in which light emitting elements and light receiving elements are combined along a distance corresponding to the width of the head as a detection section of nozzle clogging of a carriage type ink jet printer in which ink is jetted from the head in a direction (main scanning direction) perpendicularly crossing a carrying direction of a paper (sub scanning direction) to form an image (JP-Tokukai-hei-11-188853A, hereinafter referred to as “Patent Document 1”).
However, applying Patent Document 1 to a line head type ink jet printer could be causative factors of cost increase due to the needs to adjust the amount of light or the diameter of beam from the light emitting elements with high accuracy because one line head has a large length and the size of the ink droplets jetted from the nozzles is small, and to move the detection section for nozzle clogging by using a positioning sensor with high accuracy. Also, the distance between the light emitting elements and the light receiving elements becomes large, which may cause misdetection due to dust or ink droplets in the form of mist. Further, since a large number of nozzles which need to be detected exist in one line head, it would raise a problem that time for detection becomes long.